1. Technical Field
The present invention relates to an optical device including an optical modulator that modulates a light beam irradiated by a light source in accordance with image information and forms an optical image, and to a projector.
2. Related Art
Generally, a projector has been used for presentations at conferences, academic societies, exhibitions and the like as well as for home theater purposes etc. Such projector includes therein a light source, an optical modulator that modulates a light beam irradiated by the light source in accordance with image information, a color-combining optical device that combining the light beam modulated by the optical modulator and irradiates it, and a projection optical device that projects the light beam combined by the color-combining optical device in an enlarged manner.
In optical components of the projector, as for the optical modulator, an active matrix driven optical modulator is generally used, which has electrooptic material such as liquid crystal sealed between a pair of substrates. Specifically, the pair of substrates included in the optical modulator have: a driving substrate disposed on a light irradiation side and provided with a data line, a scan line, a switching element, a pixel electrode, etc. for applying driving voltage to the liquid crystal; and an opposite substrate disposed on a light incident side and provided with a common electrode, a black mask, etc. On the light incident side and the light irradiation side of the optical modulator, an incident-side polarization plate and an irradiation side polarization plate transmitting a light beam with a predetermined polarization axis are respectively disposed.
When the light beam is irradiated by the light source onto the optical modulator, the optical modulator tends to be subjected to the temperature rise due to light absorption of the data line and the scan line formed on the driving substrate and the black mask formed on the opposite substrates as well as light absorption of a liquid crystal layer. Further, out of the light beams irradiated by the light source and transmitted through the optical modulator, the light beam not having the predetermined polarization axis is absorbed by the incident-side polarization plate and the irradiation-side polarization plate, which easily causes generation of heat on the polarization plates. These polarization plates easily generate heat, but are easily affected by heat. Therefore, in order to stably form the optical image, the optical components such as the optical modulator and the polarization plates are required to be cooled effectively.
Thus, the projector including such optical components therein needs to restrain rise in the temperature of the optical components such as the optical modulator and the polarization plates. Then, there has been provided a projector equipped with an optical device that includes an optical modulator holder having a cooling chamber with cooling fluid sealed therein in order to cool optical components, a light incident side or a light irradiation side of the cooling chamber being sealed with one of substrates of the optical modulator (for instance, see Document: JP-A-2003-195254, [0006] and [0018]).
The projector realizes that the cooling fluid in the cooling chamber contacts an image formation area of the optical modulator, so that heat generated at the optical modulator due to a light beam irradiated by a light source is radiated by heat transfer on account of convention of the cooling fluid.
Additionally, a recess for collecting air bubbles is formed inside the cooling chamber of the projector to prevent air bubbles or dusts from entering into an optical path by the convection of the cooling fluid, so that the air bubbles and the like contained in the cooling fluid are collected in the recess for collecting air bubbles, thus preventing the air bubbles from facing the image formation area of the optical modulator.
However, in this configuration disclosed in the above-mentioned Document, in which the heat generated at the optical modulator is radiated by the heat transfer utilizing the convection of the cooling fluid, since the cooling fluid is sealed inside the cooling chamber, the cooling fluid becomes warm because of the optical modulator generating heat, and the warm cooling fluid stays inside the cooling chamber. Thus the cooling performance is not enough, and it is difficult to cool the optical components effectively as compared with the case that the cooling fluid is forcedly circulated.
Further, since the recess for collecting air bubbles employed in the configuration disclosed in the Document is close to the image formation area, the air bubbles etc. may enter to the image formation area. As a result, the air bubbles affect on image quality and accordingly, a clear projection image will not be formed.